[Show abstract][Hide abstract] ABSTRACT: The Drosophila Toll receptor does not interact directly with microbial determinants, but is instead activated by a cleaved form of the cytokine-like molecule Spätzle. During the immune response, Spätzle is processed by complex cascades of serine proteases, which are activated by secreted pattern-recognition receptors. Here, we demonstrate the essential role of ModSP, a modular serine protease, in the activation of the Toll pathway by gram-positive bacteria and fungi. Our analysis shows that ModSP integrates signals originating from the circulating recognition molecules GNBP3 and PGRP-SA and connects them to the Grass-SPE-Spätzle extracellular pathway upstream of the Toll receptor. It also reveals the conserved role of modular serine proteases in the activation of insect immune reactions.
Proceedings of the National Academy of Sciences 08/2009; 106(30):12442-7. · 9.74 Impact Factor